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Car Heater Blowing Cold Air – Possible Reasons And What You Should Do

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Car Heater Blowing Cold Air

Aside from being a means of transport, our cars also provide an apt level of comfort during the rides. It is hard to argue the fact that vehicles are an indispensable part of our daily life. 

When the winter hits and the temperatures drop down, we bet you love driving in the cozy cabin of your car. You turn the heater on, but are left wondering – Why is my heater blowing cold air in my car?  

Instead of just scratching your head for hours only to shill out hundreds of dollars for a mechanic later, you might want to try some fixes that we have to offer. 

We’ll also introduce you with the potential causes behind this malfunction so that you can exercise precautions later. 

Possible reasons why your heater is blowing cold air 

Low coolant level 

Coolants are 50% antifreeze and 50% water. This fluid is primarily responsible for supporting the heating system. When you crank up your heat, this coolant facilitates the heat to flow in your cabin. However, you should keep in mind that if your heater blows out cold air only for the first minute followed by throwing hot air, then that’s okay as your engine usually takes some time to heat up in winters. 

But if this persists for a longer time, then it is definitely an indication of low coolant levels which could be due to a fuel leak or problems with radiator/hoses. 

Fix : Using your vehicle’s manual, top up the coolant level to the required mark. A coolant change is generally covered within the routine maintenance cycle and can cost roughly $150-160. However, if the problem is due to a leak, then get ready to shill out $600-800. Although we would recommend that you try finding the leak location by yourself and see if you can fix it on your own. 

Thermostat impairment 

The thermostat acts as a valve in order to regulate the amount of coolant that flows to the heater core. Once you start your engine, the thermostat is turned on as soon as it reaches a threshold temperature. After this, the thermostat allows the coolant to flow down. 

Your thermostat may be either stuck open or closed. In case it is closed, the coolant engine will overheat at a faster rate and will self-destruct overtime. Needless to say, since no coolant is able to flow into the heating core, the only air you’ll be getting is cold. 

On the contrary, if the thermostat is jammed open, the coolant flow will be continuous resulting in a cold heating core. 

Fix : Installing a new thermostat. The cost of a new thermostat ranges between $30-60. Given below are the steps required to do so : 

  • Park your vehicle and ensure a stationary position 
  • Make sure that the engine is totally cooled off when you start
  • Unbolt the thermostat housing present at the end of the upper house for the radiator. 
  • Replace the faulty thermostat with a new one followed by bolting it tightly to the system. 

Malfunctioning heater core

Technician holding dirty air filter for car

A heater core with pieces of dust and lint might also be the reason why your heater is blowing cold air. Given the passage through the core is quite narrow, there’s a high probability that dirt and grime will be eventually deposited on the surface overtime. 

The fins inside the core can also easily be clogged. 

Fix : Manually cleaning the core can solve the problem in most of the cases. For the inside of the heating core, flushing the core can be quite helpful. This may cost you around a hundred to a couple hundred bucks on average. 

Jammed blend door

A jammed blend door can prohibit the hot air from passing to the cabin. Aside from this, your heat control buttons can also get jammed leading to poor air circulation. Prolonged usage often results in such problems. 

Fix : Replace the gear depending upon the model of your vehicle. 

Air bubbles in the cooling system 

The elevated position of the heater core in the system can often cause air bubbles to seep into the coolant fluid. The heat then does not get transferred properly leading to a cold heating core. 

Fix : Follow the steps given below to remove the bubbles from your coolant fluid : 

  • Notch up the heating system to the max. 
  • Remove the cap of the coolant tank and fill up the coolant till the brim. 
  • Fire the engine once, keeping the tank cap still open.
  • After a few minutes, you’ll notice that the thermostat has been turned on. 
  • Close the lid now and test your heating system. 

Working of a car heater 

Car heating systems are bifurcated into three types : Water cooled engines, air cooled engines and electric. However, since the problem that we are focusing on is more prominent in water cooled engines, let us find out how these engines work. 

Water cooled engines work based on the basic fundamentals of heat. As your engine soars up in temperature, it generates heat which then helps with the transmission of hot air into the cabin. However, constant exposure to heat may end up overheating your engine. 

To combat this issue, these engines have a component called a coolant which absorbs the heat to prevent overheating. As soon as the coolant is heated upto a couple hundred degrees, the heat flows into the thermostat through the radiator which lowers the temperature. 

In order to dissipate the hot air, a small heater core is also placed along with an inbuilt fan to blow the air out. 

To sum up, the heat generated by your engine flows through a coolant which then heats up the heater core followed by transferring the heat in the cabin through a fan. 

What if the air is warm, but not hot enough? 

Low level of heat may be due to loose plugins somewhere inside your system. Furthermore, your thermostat could also be stuck causing the low of hot coolant into your heater core. This results in a warm hue of air instead of a hot burst. 

In case your thermostat is stuck in a partially open position, the heater core may not get enough supply of coolant. Additionally, as your car ages, the heater core may also end up capturing little tid bits of dirt and grime leading to a blockage which impairs/slows down its functioning. 

Not to worry though, as this issue can be easily eradicated by regular maintenance and a coolant change on a regular basis. 

Regular maintenance goes a long way 

Majority of issues related to your engine and cooling systems can be resolved if you keep changing your fluid on a regular basis. This also improves the quality of your transmission. Given that a transmission replacement may cost you anything between $2000 – $6000, it is only wise to spend a portion of this amount in regular intervals instead. 

Other important upgrades that you should administer on a timely basis are : 

  • OEM oil changes, quarterly 
  • Tire rotations, twice every year 
  • Engine bad transmission checks, quarterly 

Now that you know the real reason behind the cold air coming out of your car heater, you can save yourself from withering in a rough winter. Most of these issues can be fixed without any assistance while some need a professsional’s expertise. 

But if you are an individual for whom comfort is a priority, then these upgrades and fixes will totally seem worth your penny. 

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